A review of Colletieae and Discaria (Rhamnaceae) in Australia

Published online: 22 Dec. 2020The tribe Colletieae (Rhamnaceae) is reviewed for Australia. It is primarily South American, but two species of Discaria Hook., D. pubescens (Brongn.) Druce and D. nitida Tortosa, occur in south-eastern Australia and Tasmania. The two species are described and illustrated. A hybrid taxon sometimes occurs in areas where the two species are sympatric. The history and typification of the name D. pubescens and its synonyms is discussed and clarified.Jürgen Kellermann and Frank Udovici

A High Resolution Genetic Map Anchoring Scaffolds of the Sequenced Watermelon Genome

As part of our ongoing efforts to sequence and map the watermelon (Citrullus spp.) genome, we have constructed a high density genetic linkage map. The map positioned 234 watermelon genome sequence scaffolds (an average size of 1.41 Mb) that cover about 330 Mb and account for 93.5% of the 353 Mb of the assembled genomic sequences of the elite Chinese watermelon line 97103 (Citrullus lanatus var. lanatus). The genetic map was constructed using an F8 population of 103 recombinant inbred lines (RILs). The RILs are derived from a cross between the line 97103 and the United States Plant Introduction (PI) 296341-FR (C. lanatus var. citroides) that contains resistance to fusarium wilt (races 0, 1, and 2). The genetic map consists of eleven linkage groups that include 698 simple sequence repeat (SSR), 219 insertion-deletion (InDel) and 36 structure variation (SV) markers and spans ∼800 cM with a mean marker interval of 0.8 cM. Using fluorescent in situ hybridization (FISH) with 11 BACs that produced chromosome-specifc signals, we have depicted watermelon chromosomes that correspond to the eleven linkage groups constructed in this study. The high resolution genetic map developed here should be a useful platform for the assembly of the watermelon genome, for the development of sequence-based markers used in breeding programs, and for the identification of genes associated with important agricultural traits

Oldest Known Eucalyptus Macrofossils Are from South America

The evolutionary history of Eucalyptus and the eucalypts, the larger clade of seven genera including Eucalyptus that today have a natural distribution almost exclusively in Australasia, is poorly documented from the fossil record. Little physical evidence exists bearing on the ancient geographical distributions or morphologies of plants within the clade. Herein, we introduce fossil material of Eucalyptus from the early Eocene (ca. 51.9 Ma) Laguna del Hunco paleoflora of Chubut Province, Argentina; specimens include multiple leaves, infructescences, and dispersed capsules, several flower buds, and a single flower. Morphological similarities that relate the fossils to extant eucalypts include leaf shape, venation, and epidermal oil glands; infructescence structure; valvate capsulate fruits; and operculate flower buds. The presence of a staminophore scar on the fruits links them to Eucalyptus, and the presence of a transverse scar on the flower buds indicates a relationship to Eucalyptus subgenus Symphyomyrtus. Phylogenetic analyses of morphological data alone and combined with aligned sequence data from a prior study including 16 extant eucalypts, one outgroup, and a terminal representing the fossils indicate that the fossils are nested within Eucalyptus. These are the only illustrated Eucalyptus fossils that are definitively Eocene in age, and the only conclusively identified extant or fossil eucalypts naturally occurring outside of Australasia and adjacent Mindanao. Thus, these fossils indicate that the evolution of the eucalypt group is not constrained to a single region. Moreover, they strengthen the taxonomic connections between the Laguna del Hunco paleoflora and extant subtropical and tropical Australasia, one of the three major ecologic-geographic elements of the Laguna del Hunco paleoflora. The age and affinities of the fossils also indicate that Eucalyptus subgenus Symphyomyrtus is older than previously supposed. Paleoecological data indicate that the Patagonian Eucalyptus dominated volcanically disturbed areas adjacent to standing rainforest surrounding an Eocene caldera lake

Large indels obscure phylogeny in analysis of chloroplast DNA (trnL-F) sequence data: Pomaderreae (Rhamnaceae) revisited

Phylogenetic analysis of 69 ingroup-taxa of Pomaderreae using trnL-F sequences confirm the monophyly of the tribe. The analysis was impeded by a paucity of informative characters and the presence of apparently homoplasious indel characters and base changes within the P8 region of the trnL intron: the strict consensus tree of the trnL-F analysis is less resolved and had fewer supported clades than in a previous ITS analysis (Kellermann et al. 2005). The backbone of the cladogram is not supported and relationships between genera/clades are somewhat uncertain. The genera Cryptandra, Stenanthemum and Polianthion are well supported. Pomaderris groups with Siegfriedia and Trymalium, but only individual clades within these genera receive support. Blackallia biloba is related to two atypical species of Stenanthemum and B. connata to Cryptandra, but this grouping depends on the exclusion of homoplasious indel characters. Species of Spyridium only group in one clade when these indels are excluded, otherwise they are located in a polytomy at the base of the cladogram. The results mostly agree with earlier findings using ITS sequence data. Two new genera containing atypical species of Stenanthemum are suggested. A synopsis of the Australian genera of Rhamnaceae is provided.Jürgen Kellermann and Frank Udovici

New combinations in Callistemon (Myrtaceae)

Volume: 30Start Page: 23End Page: 2

Successful DNA amplification from Acacia (Leguminosae) and other refractory Australian plants and fungi using a nested/semi-nested PCR protocol

Volume: 16Start Page: 47End Page: 5

Divergent lineages in a semi-arid mallee species, Eucalyptus behriana, correspond to a major geographic break in southeastern Australia

Aim: To infer relationships between populations of the semi-arid, mallee eucalypt, Eucalyptus behriana, to build hypotheses regarding evolution of major disjunctions in the species' distribution and to expand understanding of the biogeographical history of southeastern Australia. Location: Southeastern Australia. Taxon: Eucalyptus behriana (Myrtaceae, Angiospermae). Methods: We developed a large dataset of anonymous genomic loci for 97 samples from 11 populations of E. behriana using double digest restriction site-associated DNA sequencing (ddRAD-seq), to determine genetic relationships between the populations. These relationships, along with species distribution models, were used to construct hypotheses regarding environmental processes that have driven fragmentation of the species' distribution. Results: Greatest genetic divergence was between populations on either side of the Lower Murray Basin. Populations west of the Basin showed greater genetic divergence between one another than the eastern populations. The most genetically distinct population in the east (Long Forest) was separated from others by the Great Dividing Range. A close relationship was found between the outlying northernmost population (near West Wyalong) and those in the Victorian Goldfields despite a large disjunction between them. Conclusions: Patterns of genetic variation are consistent with a history of vicariant differentiation of disjunct populations. We infer that an early disjunction to develop in the species distribution was that across the Lower Murray Basin, an important biogeographical barrier separating many dry sclerophyll plant taxa in southeastern Australia. Additionally, our results suggest that the western populations fragmented earlier than the eastern ones. Fragmentation, both west and east of the Murray Basin, is likely tied to climatic changes associated with glacial-interglacial cycles although it remains possible that major geological events including uplift of the Mount Lofty Ranges and basalt flows in the Newer Volcanics Province also played a role